Methods and apparatus for antenna isolation-dependent coexistence in wireless systems

ABSTRACT

Methods and apparatus for selectively switching one or more antennas in a multiple-input, multiple-output (MIMO) antenna array so as to mitigate interference with another RF interface within the same space-constrained device, based on radio frequency isolation. In one embodiment, the MIMO interface comprises a WLAN interface having a 2×2 or 3×3 array of antennae which are placed in a wireless device in an asymmetric fashion with respect to the antenna of the second interface, and the other interface comprises a PAN (e.g., Bluetooth) interface operating in an overlapping frequency band (e.g., ISM band). When both interfaces are operating, interference is mitigated through selectively switching off one or more of the MIMO antennae, and using the remaining antenna(e) having the best isolation from the Bluetooth antennae. This approach allows simultaneous operation of both interferences without significant degradation to user experience or the operation of either interface, and may also provide power savings critical to mobile device battery longevity.

RELATED APPLICATIONS

This application is related to co-owned and co-pending U.S. patentapplication Ser. No. 12/006,992 filed Jan. 7, 2008 and entitled “Methodsand Apparatus for Wireless Device Coexistence” and Ser. No. 12/082,586filed Apr. 11, 2008 entitled “Methods And Apparatus For Network CapacityEnhancement For Wireless Device Coexistence”, each of the foregoingincorporated herein by reference in its entirety.

COPYRIGHT

A portion of the disclosure of this patent document contains materialthat is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent files or records, but otherwise reserves all copyrightrights whatsoever.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates generally to the field of wirelesscommunication and data networks. More particularly, in one exemplaryaspect, the present invention is directed to wireless communicationssystem using multiple air interfaces and multiple antennas, including amultiple-in, multiple-out (MIMO) antenna.

2. Description of Related Technology

Wireless connectivity is becoming ubiquitously available and necessaryin computing and entertainment products. Presently, manytelecommunications products such as mobile phones, computers, mediaplayers, etc. come equipped with one or more wireless networking orcommunication interfaces.

In many cases, these network interfaces may include both wired andwireless network interfaces. Wireless network interfaces, also called“air interfaces”, are of increasing interest due to the mobility andfreedom they afford a user. Exemplary wireless networking technologiesinclude WiFi (IEEE Std. 802.11a/b/g/n), WiMAX (IEEE Std. 802.16), PAN(IEEE Std. 802.15), IrDA, ultra wide band (UWB), Mobile Wideband (MWBA;IEEE-Std. 802.20), and others.

To increase the transmission bitrates of a wireless system, use ofmultiple antennae for transmission/reception has gained popularity. Suchsystems are called multiple-in, multiple-out systems (MIMO) and mayemploy multiple transmitting or multiple receiving antennae or both.See, e.g., IEEE-Std. 802.11n, which employs a MIMO approach in thecontext of a WLAN environment, as well as IEEE-Std. 802.16e (WiMAX),each of the foregoing being incorporated herein by reference in itsentirety.

As a result of the growth in the total number of antennae used incommunication, both due to multiple air interfaces and due to MIMOantenna systems, designers of hardware platforms are faced with achallenging task of optimal antenna placement. The problem isexacerbated when the form factor of a hardware platform is small orotherwise dimensionally or spatially constrained, thus giving a designerless flexibility in placing antennae on the hardware platform. Moreover,other factors which can affect antenna isolation and/or placement,including the use of a metallic housing or case for the device, presentadditional challenges.

Furthermore, since several radios have to support multiple bands, suchas WLAN and WiMAX, the antenna size typically cannot be compromised toachieve acceptable performance.

Additionally, since certain isolation is required in order to obtainacceptable MIMO performance, extra burden is added to the design processin order to separate the antennas sufficiently to provide suchisolation, even if these antennas are for the same radio.

One salient reason why antenna placement is of critical importancerelates to the potential electromagnetic interference between two (ormore) antennae. This interference may occur because these two antennaemay be carrying communication data over two different air interfaces ona hardware platform, and may be using the same portion of the radiofrequency spectrum (or spectrum portions close enough to createinterference). For example, Bluetooth and IEEE-Std. 802.11n devices bothoperate in the 2.4-2.8 GHz Industrial-Scientific-Medical (ISM) band, andcould potentially cause radio interference with one another. Similarly,WiMAX supports 2.3 GHz and 2.5 GHz bands; since WiMAX utilizes acomparatively high transmitter power, it can degrade Bluetoothperformance significantly if the antenna isolation is not sufficientlyhigh.

The degree of isolation between potentially interfering antennae impactsthe severity of the interference problem. Isolation is generally afunction of path loss, or attenuation, suffered by radio frequency (RF)signals from one antenna to the other. If the isolation between antennaeof one air interface and antennae of another air interface issufficiently large, then the interference with one another may benegligible. What is “sufficiently large” isolation may be implementationspecific, and may depend on several factors such as receiversensitivity.

In cases where the isolation is sufficiently large (e.g., >35 db betweenthe first and second air interface antennae), solutions such as theadaptive frequency hopping (AFH) feature of Bluetooth can be employed toprovide largely unencumbered simultaneous operation of the twointerfaces (e.g., Bluetooth and WLAN).

However, when the isolation between an antenna pair is not sufficientlylarge (e.g., when the isolation from both antennas from one radio is notsufficiently large with respect to the other radio, such as for WLAN andBluetooth coexistence cases where both WLAN antennas have less than 30dB isolation with Bluetooth antenna), the multiple air interfaces maysignificantly interfere with each other's transmission. It is clearlydesirable to mitigate such interference so as to avoid adverse effectson user experience (e.g., Bluetooth audio drop-outs during A2DPstreaming playback, slow WLAN and Bluetooth transfer speeds, WLAN linkdrops, poor Bluetooth mouse tracking, streaming video jitter, etc.). Onesimple solution in prior art is to time-share or time-division multiplexthe use of potentially interfering interfaces—that is, turn off oneinterface while the other interface is actively transmitting orreceiving. However, this solution suffers from the drawback that it mayresult in an annoying and unsatisfactory user experience, wherein dataconnectivity on one interface may be broken or intermittent due toactivity on the other air interface. For example, speech on a Bluetoothinterface may come across segmented or choppy if the interface has totime-division multiplex with a WLAN air interface that is carrying dataor voice communication on its air interface.

Other solutions have been proposed as well, including using antennaisolation for selecting transmit and receive antennas. For example, U.S.Pat. No. 6,774,864 to Evans, et al, entitled “Method of operating awireless communications system,” issued Aug. 10, 2004 discloses a methodof selecting a combination of transmit antennas and receive antennas ina MIMO antenna system to give the best isolation from adjacent parallelsignal streams comprises transmitting a first signal from one of thetransmit antennas and measuring a quality metric, for example signalstrength of the received signal at each of the receive antennas. Theprocess is repeated using signals transmitted in turn by each theremaining transmit antennas. A channel matrix is compiled of thetransmit antennas versus the receive antennas and a selection is made ofa combination of transmit and receive antennas receiving acceptably afirst signal and unacceptably a second signal and vice versa. Theselected combination is used to send and receive MIMO signals. Switchesare provided for coupling the selected antennas to the respectivetransmitters and receivers.

U.S. Pat. No. 7,366,244 to Gebara, et al. issued Apr. 29, 2008, andentitled “Method and system for antenna interference cancellation”discloses a wireless communication system which can comprise two or moreantennas that interfere with one another via free space coupling,surface wave crosstalk, dielectric leakage, or other interferenceeffect. The interference effect can produce an interference signal onone of the antennas. A cancellation device can suppress antennainterference by generating an estimate of the interference signal andsubtracting the estimate from the interference signal. The cancellationdevice can generate the estimate based on sampling signals on an antennathat generates the interference or on an antenna that receives theinterference. The cancellation device can comprise a model of thecrosstalk effect. Transmitting test signals on the communication systemcan define or refine the model.

U.S. Pat. No. 7,362,275 to Tu, et al. issued Apr. 22, 2008 and entitled“Internal antenna and mother board architecture” discloses variousembodiments of an internal antenna and motherboard architecture. In oneembodiment, a wireless device may include a housing enclosing a firstmotherboard and a second motherboard. The ground plane of the firstmotherboard may be coupled to the ground plane of the second motherboardwithin the housing. The first motherboard and the second motherboard mayact as an internal antenna system for the wireless device.

U.S. Pat. No. 7,359,730 to Dennis, et al. issued Apr. 15, 2008 andentitled “Method and apparatus for reducing interference associated withwireless communication” discloses a method and apparatus for reducinginterference associated with wireless communication in an area havingsensitive electronic equipment. A wireless communications devicereceives, from an access point, a signal having a signal strength abovea predetermined threshold. The wireless communications device determinesa transmission power level maximum based on the received signal and thentransmits a signal to the access point at a transmission power level ator below the transmission power level maximum. The wirelesscommunications device disables the transmission when the signal strengthfalls below the predetermined threshold.

U.S. Pat. No. 7,352,332 to Betts-LaCroix, et al. issued Apr. 1, 2008 andentitled “Multiple disparate wireless units sharing of antennas”discloses, in one embodiment, an apparatus including, but is not limitedto, a first wireless communication unit of a first wirelesscommunication standard, where the first standard includes selecting oneof two antennas provided. The apparatus further includes a secondwireless communication unit of a second wireless communication standard,where a first antenna and a second antenna are shared by the first andsecond communication units. Other methods and apparatuses are alsodescribed.

U.S. Pat. No. 7,295,860 to Suwa issued Nov. 13, 2007 and entitled “Radiocommunication apparatus” discloses a radio communication apparatus whichcomprises a radio unit capable of transmitting or receiving a firstradio communication signal of a Bluetooth standard and a second radiocommunication signal of a cordless phone standard and a synchronismdiscriminator for discriminating a radio communication standard signal.The radio communication apparatus switches between first and secondradio communication modes in response to a discrimination result of thesynchronism discriminator, detects a type and a weight of a sound errorevery mode, and adds or subtracts the weight of the sound error in apresent slot to or from a weight of a sound error in the previous slotin response to a degree of the sound error in the present slot. Thisstructure allows a single apparatus to transmit or receive both of twokinds of radio communication standard signals, and the sound error isadequately and precisely handled in response to the type and weight ofthe sound error, thereby improving quality of the sound signalcancellation.

U.S. Pat. No. 7,253,783 to Chiang, et al. issued Aug. 7, 2007 andentitled “Low cost multiple pattern antenna for use with multiplereceiver systems” discloses an antenna assembly including at least twoactive or main radiating omni-directional antenna elements arranged withat least one beam control or passive antenna element used as areflector. The beam control antenna element(s) may have multiplereactance elements that can electrically terminate it to adjust theinput or output beam pattern(s) produced by the combination of theactive antenna elements and the beam control antenna element(s). Morespecifically, the beam control antenna element(s) may be coupled todifferent terminating reactances to change beam characteristics, such asthe directivity and angular beamwidth. Processing may be employed toselect which terminating reactance to use. Consequently, the radiatorpattern of the antenna can be more easily directed towards a specifictarget receiver/transmitter, reduce signal-to-noise interference levels,and/or increase gain. A Multiple-Input, Multiple-Output (MIMO)processing technique may be employed to operate the antenna assemblywith simultaneous beam patterns.

U.S. Pat. No. 7,142,864 to Laroia, et al. issued Nov. 28, 2006 andentitled “Methods and apparatus of enhancing performance in wirelesscommunication systems” discloses methods and apparatus for supportingand using multiple communications channels corresponding to differenttransmit technologies and/or access technologies in parallel within acell of a wireless communications system. Mobile nodes support multipletechnologies and can switch between the technology being used at aparticular point in time, e.g., from a first channel corresponding to afirst technology to a second channel corresponding to a differenttechnology which provides better transmission characteristics, e.g., abetter perceived channel quality. Mobiles maintain at least two sets ofchannel quality information at any one point in time. Mobiles select thebetter channel and communicate the channel selection to the base stationor communicate channel quality information for multiple channels to thebasestation and allow the base station to select the channelcorresponding to the technology providing the better conditions for themobile. Different mobiles in the same cell may support differenttechnologies.

United States Patent Publication No. 20080095263 to Xu et al. publishedApr. 24, 2008 entitled “Method And Apparatus For Selection MechanismBetween OFDM-MIMO And LFDM-SIMO” discloses systems and methodologiesthat facilitate switching between various combinations of MIMO, SIMO,SISO and OFDM, LFDM and IFDM. According to various aspects, a method fora wireless communication network is provided that includes: receiving afirst set of data information, wherein the first set of informationcomprising a first value, determining if the first value is above athreshold and transmitting an indication to switch to using a firsttransmission technique if determined that the first value is above thethreshold.

United States Patent Publication No. 20070238483 to Boirequ et. alpublished Oct. 11, 2007 entitled “Antenna sharing techniques” disclosesa mobile computing device may comprise an antenna, a switch to couple tothe antenna, and multiple transceivers to couple to the switch. Themobile computing device may also comprise an antenna management moduleto couple to the switch and the transceivers. The antenna managementmodule may control the switch to electrically connect one of thetransceivers to the antenna. Other embodiments may be described andclaimed.

United States Patent Publication No. 20070076649 to Lin et. al publishedApr. 5, 2007 entitled “Techniques for heterogeneous radio cooperation”discloses a cooperative communications manager module which establishesa first wireless link with a client device using a first channelfrequency and dispatches a first message to the client device over thefirst channel frequency. The cooperative communications manager moduleestablishes a second wireless link with a destination node and controlsthe cooperative transmission of the first message simultaneously withthe client device to the destination node over the second wireless linkusing a second channel frequency.

United States Patent Publication No. 20060223450 published Oct. 5, 2006to Dacosta et al. entitled “Method and apparatus to resist fading inMIMO and SIMO wireless systems” discloses a wireless communicationsystem, the receiver includes a first plurality of receive chains and asecond plurality of antennas. Each receive chain is selectivelyconnectable to selected antennas. The antennas are selected based oncriteria obtained from a received RF signal to produce an antennaconfiguration connected to the receive chains to reduce RF fading at thereceiver. An electronic switch connects the antennas to the receivechains. The receiver is programmed to determine which antenna should beconnected to each receive chain by the switch by measuringcharacteristics of the received signal for each allowed antennaconfiguration and selecting the best antenna configuration. Transmittersmay be similarly configured.

United States Patent Publication No. 20060034217 published Feb. 16, 2006to Kwon et al. entitled “Method and network device for enabling MIMOstation and SISO station to coexist in wireless network without datacollision” discloses a method of enabling a multi-input multi-output(MIMO) station and a single input single output (SISO) station tocoexist in a wireless network and a wireless network device. The methodincludes receiving information on a station when the station accesses awireless network, setting coexistence information by comparing a numberof antennas of the station accessing the wireless network with a numberof antennas of a plurality of stations constituting the wirelessnetwork, and transmitting a frame containing the coexistence informationto the plurality of stations constituting the wireless network.

Despite the foregoing variety of approaches to MIMO and multiple airinterface co-existence, there is a need for an improved method andapparatus for mitigating potential interference between antennae ofdifferent air interfaces on the same hardware platform. Specifically, asalient need exists for a solution which addresses platforms that arehighly space-constrained or otherwise necessarily result in lowisolation values between the antennae of the various air interfaces ofthe platform (for example, WiFi/WLAN and Bluetooth, WiMAX and Bluetooth,WLAN and UWB). Such an improved solution would ideally permit for gooduser experience (i.e., devoid of any significant audio or datadrop-outs, effects on data streaming rate, preclusion of use of oneinterface when another is being used, and so forth which would adverselyaffect user satisfaction) and be absent significant operationrestrictions with respect to the multiple air interfaces (e.g., allowtwo or more interfaces to operate simultaneously in at least partialcapacity), while still obeying the platform or form-factor limitationssuch as those present in extremely small hand-held or laptop computingdevices, or those with metallic cases which inherently presentchallenges to antenna placement.

SUMMARY OF THE INVENTION

The present invention satisfies the aforementioned needs by providingimproved apparatus and methods for air interface coexistence.

In a first aspect of the invention, a method of operating a wirelessdevice having at least first and second air interfaces is disclosed. Inone embodiment, the first air interface comprises at least two antennaelements, the second interface comprising another antenna element, andthe method comprises: determining the isolation between individual onesof the at least two antenna elements of the first interface and theanother antenna element of the second interface; selecting at least oneof the at least two elements of the first interface for operation; andsimultaneously operating the first and second interfaces within a commonfrequency band using the selected one of the at least two elements ofthe first interface, and the another element of the second interface,respectively.

In one variant, the isolation between the first antenna element of theat least two antenna elements of the first interface and the anotherantenna element of the second interface is substantially unequal to thatbetween the second antenna element and the another antenna element.

In another variant, the first interface comprises a high data rate WLANinterface, and the second interface comprises a lower data rate personalarea networking (PAN) interface, and the simultaneously operatingcomprises operating within a band comprising a frequency of 2.4 GHz. Theact of selecting comprises operating one antenna element circuitassociated with the selected antenna element, and not operating theantenna element circuit associated with the non-selected ones of the atleast two elements.

In yet another variant, the simultaneous operation comprisessimultaneously operating without use of a time-sharing or time-dividedspectral access scheme.

In a further variant, the placement of the at least two antenna elementsof the first interface and the another antenna element of the secondinterface within the wireless device does not permit isolation levelsbetween the at least two elements and the another element sufficient forsimultaneous operation of all of the at least two elements and theanother element without significant degradation of the data rate of theWLAN interface.

In a second aspect of the invention, a method of operating aMIMO-capable air interface of a device is disclosed. In one embodiment,the device has at least one additional air interface, and the methodcomprises: communicating from the one other air interface to theMIMO-capable interface communication activity level on the one other airinterface; if the MIMO-capable interface and the one other air interfaceare operating simultaneously, then determining a radio frequencyisolation between the at least two antenna elements of the MIMO-capableinterface and the one other air interface; and based at least in part onthe communicated activity level and the determined isolation,configuring the MIMO-capable interface to operate a first number of theantenna elements.

In one variant, the determining comprises determining a staticisolation.

In another variant, the determining is responsive to physical layout ofantennae of the device.

In yet another variant the determining comprises determining atime-variant isolation.

In still a further variant, the determining is based at least in part onan attenuator setting. The attenuator setting is obtained from front endradio circuitry of at least one of the MIMO-capable interface and theone additional interface.

In another variant, the communicating comprises communicating using ahardware-based signal.

Alternatively, the communicating may comprise communicating using asoftware message.

In another variant, the method further comprises classifying the radiofrequency isolation as one of symmetric or asymmetric. If the radiofrequency isolation is classified as asymmetric, then the first numberof antenna elements is 1.

In a third aspect of the invention, apparatus having multiple airinterfaces is disclosed. In one embodiment, the apparatus comprises: aplurality of first antenna elements configured to communicate on a firstair interface; at least one second antenna element configured tocommunicate on a second air interface; first front end circuitryoperatively coupled with the plurality of first antenna elements, thecircuitry enabling transmitting and receiving signals over the firstinterface; second front end circuitry operatively coupled with the atleast one second antenna element, the second circuitry enablingtransmitting and receiving signals over the second interface; acommunication channel between the interface and the second interface andadapted to carry activity information; and a processor communicativelycoupled to the first front end circuit and the second front end circuit.The processor is configured to: determine the isolation between antennaepairs formed from the plurality of first antenna elements and the atleast one second antenna element; evaluate whether the isolations aresymmetric or asymmetric; and based at least in part on the evaluation,not using of at least one antenna element from the plurality of firstantennae.

In one variant, the first front end circuitry comprises front endcircuits for each of the antenna elements of the plurality, and the notusing comprises turning off at least a portion of the front endcircuits.

In another variant, the not using comprises not using if the isolationsare evaluated to be asymmetric.

In a further variant, the apparatus comprises a portable computerizeddevice having a substantially metallic outer case.

In another variant, the first interface comprises a WLAN interfacehaving MIMO capability, and the second interface comprises a personalarea network (PAN) interface. The placement of the plurality of firstantenna elements of the WLAN interface and the at last one secondantenna element of the PAN interface within the apparatus does notpermit isolation levels between the plurality of first elements and theat least one second element sufficient for simultaneous operation of allof the plurality of first elements and the at least one second elementwithout significant degradation of the data rate of the WLAN interface.

In yet a further variant, the processor is configured to detect theisolations as a function of at least one of: (i) the physical placementof the plurality of first antenna elements; (ii) an operational settingof the first front end circuitry; and (iii) an operational setting ofthe second front end circuitry.

In yet another variant, wherein the communication channel comprises oneor more hardware-based channels adapted to carry signals from the secondinterface to the first interface.

In a fourth aspect of the invention, wireless portable apparatus adaptedfor data communication over first and second air interfaces isdisclosed. In one embodiment, the apparatus comprises: a first airinterface having at least two antennae associated therewith; a secondair interface having at least one antenna associated therewith, thefirst and second air interfaces operating in a substantially overlappingfrequency band, the at least two antenna of the first interface beingdisposed within the apparatus asymmetrically with respect to theirisolations with the at least one antenna of the second interface; aprocessor; and a storage device, the storage device comprising acomputer program having a plurality of instructions that when executed:determine if the potential for interference between the first and secondair interfaces exists; and if the potential exists, turning at least oneof the at least two antennae off so as to mitigate the interference.

In one variant, the first interface comprises a MIMO wireless LAN (WLAN)interface; the second interface comprises a personal area networking(PAN) interface; and the turning at least one of the at least twoantenna off comprises disabling transmission or reception via one of theat least two antennae that has the lowest isolation with the at leastone antenna of the PAN interface.

In another variant, the apparatus comprises a portable computerizeddevice having a clamshell-like outer case, and the at least two antennaeof the WLAN interface and the at least one antenna of the secondinterface are all disposed substantially within a hinge region of theclamshell-like case.

In a further variant, the outer case is substantially metallic.

In yet another variant, the determination of the potential forinterference comprises determining whether both first and secondinterfaces are transmitting or receiving at the same time.

In a fifth aspect of the invention, a computer readable apparatus havinga storage medium is disclosed. In one embodiment, the medium is adaptedto store a computer program comprising instructions which, whenexecuted: detect an asymmetric isolation condition by comparing theisolations between antennae of a plurality of antenna pairs associatedwith first and second air interfaces; and turns on or off, responsive tothe asymmetric condition, use of at least one antenna within the firstinterface, the first interface comprising a multi-input, multi-output(MIMO) air interface.

In a sixth aspect of the invention, a method of doing business relatingto a wireless device is disclosed. In one embodiment, the methodcomprises: receiving a plurality of user inputs regarding a desiredconfiguration of the device; based at least in part on the inputs,determining the placement of a plurality of antennae within the device,the plurality of antenna comprising two or more antennae associated witha MIMO-enabled air interface and one or more antennae associated with asecond air interface; and configuring the device during build so as toselectively activate or deactivate at least one of the two or moreantennae during conditions of simultaneous operation of the MIMO-enabledand second air interfaces so as to mitigate the effects of interferencethere between.

In one variant, the act of receiving comprises receiving the inputs viaan Internet website.

In another variant, the act of receiving comprises receiving the inputsrequiring the device to have at least the MIMO-enabled interface and thesecond interface, the MIMO-enabled interface comprising a WLAN interfacecompliant with IEEE-Std. 802.11n, and the second interface comprising aPAN interface capable of operating in substantially the same frequencyspectrum as the MIMO-enabled interface.

In a further variant, the act of determining the placement comprisesdetermining a placement wherein the isolation between individual ones ofthe two or more antenna of the MIMO-enabled interface and the one ormore antennae of the second interface is not equal.

In yet another variant, the act of determining the placement is based atleast in part on isolation values obtained during testing of a prototypeof the device, the prototype having a substantially similarconfiguration to that of the wireless device as requested by the user.

In a seventh aspect of the invention, a method of operating a devicehaving at least first and second air interfaces is disclosed. In oneembodiment, the method includes: communicating on the first airinterface via a plurality of first antenna elements, communicating onthe second air interface via at least one second antenna element,determining the isolation isolations between antennae pairs formed fromthe plurality of first antenna elements and the at least one secondantenna element, and evaluating whether the isolations are symmetric orasymmetric. Based at least in part on the evaluation, a subset of theplurality of first antennae antenna elements is enabled. The first andsecond air interfaces are in one variant additionally coordinatingactivity information via a distinct communication channel.

Other features and advantages of the present invention will immediatelybe recognized by persons of ordinary skill in the art with reference tothe attached drawings and detailed description of exemplary embodimentsas given below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing exemplary placement of antennae havingsymmetric isolation among various constituent antenna pairs.

FIG. 2 is a block diagram showing exemplary placement of antennae havingasymmetric isolation among various constituent antenna pairs.

FIG. 3 is a logical flowchart showing one embodiment of a generalizedmethod of providing coexistence in a wireless device with asymmetricantenna isolations in accordance with the present invention.

FIG. 3 a is a logical flowchart illustrating one alternate embodiment ofthe methodology of FIG. 3.

FIG. 4 is an X-Y plot showing bitrates achieved in an exemplarysingle-in, single-out (SISO) receive operation of a wireless device withmultiple air interfaces as compared to multiple antenna (MIMO) operationfor the same device.

FIG. 5 is an X-Y plot showing bitrates achieved in an exemplarysingle-in, single-out (SISO) transmit operation of a wireless devicewith multiple air interfaces as compared to multiple antenna (MIMO)operation for the same device.

FIG. 6 is a block diagram showing the functional relationships ofcomponents within an exemplary wireless device implemented in accordancewith one embodiment of the present invention.

FIG. 7 is a block diagram showing an exemplary test setup useful with,inter alia, the present invention.

FIG. 8 is a logical flow diagram illustrating one embodiment of abusiness methodology relating to the MIMO/SISO switching andoptimization techniques of the invention.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the term “Bluetooth” refers without limitation to anydevice, software, interface or technique that complies with one or moreof the Bluetooth technical standards, including Bluetooth CoreSpecification Version 1.2, Version 2.0, and Version 2.1+ EDR.

As used herein, the terms “client device”, “end user device” and “UE”include, but are not limited to cellular telephones, smartphones (suchas for example an iPhone™), personal computers (PCs), such as forexample an iMac™, Mac Pro™, Mac Mini™ or MacBook™, and minicomputers,whether desktop, laptop, or otherwise, as well as mobile devices such ashandheld computers, PDAs, video cameras, set-top boxes, personal mediadevices (PMDs), such as for example an iPod™, or any combinations of theforegoing.

As used herein, the term “computer program” or “software” is meant toinclude any sequence or human or machine cognizable steps which performa function. Such program may be rendered in virtually any programminglanguage or environment including, for example, C/C++, Fortran, COBOL,PASCAL, assembly language, markup languages (e.g., HTML, SGML, XML,VoXML), and the like, as well as object-oriented environments such asthe Common Object Request Broker Architecture (CORBA), Java™ (includingJ2ME, Java Beans, etc.), Binary Runtime Environment (BREW), and thelike.

As used herein, the term “circuitry” refers to any type of device havingany level of integration (including without limitation ULSI, VLSI, andLSI) and irrespective of process or base materials (including, withoutlimitation Si, SiGe, CMOS and GaAs). ICs may include, for example,memory devices (e.g., DRAM, SRAM, DDRAM, EEPROM/Flash, and ROM), digitalprocessors, SoC devices, FPGAs, ASICs, ADCs, DACs, transceivers, memorycontrollers, and other devices, as well as any combinations thereof.

As used herein, the term “memory” includes any type of integratedcircuit or other storage device adapted for storing digital dataincluding, without limitation, ROM. PROM, EEPROM, DRAM, SDRAM, DDR/2SDRAM, EDO/FPMS, RLDRAM, SRAM, “flash” memory (e.g., NAND/NOR), andPSRAM.

As used herein, the terms “microprocessor” and “digital processor” aremeant generally to include all types of digital processing devicesincluding, without limitation, digital signal processors (DSPs), reducedinstruction set computers (RISC), general-purpose (CISC) processors,microprocessors, gate arrays (e.g., FPGAs), PLDs, reconfigurable computefabrics (RCFs), array processors, secure microprocessors, andapplication-specific integrated circuits (ASICs). Such digitalprocessors may be contained on a single unitary IC die, or distributedacross multiple components.

As used herein, the terms “network” and “bearer network” refer generallyto any type of data, telecommunications or other network including,without limitation, data networks (including MANs, PANs, WANs, LANs,WLANs, micronets, piconets, internets, and intranets), hybrid fiber coax(HFC) networks, satellite networks, cellular networks, and telconetworks. Such networks or portions thereof may utilize any one or moredifferent topologies (e.g., ring, bus, star, loop, etc.), transmissionmedia (e.g., wired/RF cable, RF wireless, millimeter wave, optical,etc.) and/or communications or networking protocols (e.g., SONET,DOCSIS, IEEE Std. 802.3, 802.11, ATM, X.25, Frame Relay, 3GPP, 3GPP2,WAP, SIP, UDP, FTP, RTP/RTCP, H.323, etc.).

As used herein, the terms “network interface” or “interface” typicallyrefer to any signal, data, or software interface with a component,network or process including, without limitation, those of the FireWire(e.g., FW400, FW800, etc.), USB (e.g., USB2), Ethernet (e.g., 10/100,10/100/1000 (Gigabit Ethernet), 10-Gig-E, etc.), MoCA, Serial ATA (e.g.,SATA, e-SATA, SATAII), Ultra-ATA/DMA, Coaxsys (e.g., TVnet™), radiofrequency tuner (e.g., in-band or OOB, cable modem, etc.), WiFi(802.11a,b,g,n), WiMAX (802.16), PAN (802.15), IrDA or other wirelessfamilies.

As used herein, the term “WiFi” refers to, without limitation, any ofthe variants of ANSI/IEEE-Std. 802.11 (“Informationtechnology—Telecommunications and information exchange betweensystems—Local and metropolitan area networks—Specific requirements—Part11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY)Specifications”) or related standards including 802.11 a/b/e/g/n, eachof the foregoing being incorporated herein by reference in its entirety.

As used herein, the term “wireless” means any wireless signal, data,communication, or other interface including without limitation WiFi,Bluetooth™, 3G, HSDPA/HSUPA, TDMA, CDMA (e.g., IS-95A, WCDMA, etc.),FHSS, DSSS, GSM, PAN/802.15, WiMAX (802.16), MWBA (802.20),narrowband/FDMA, OFDM, PCS/DCS, analog cellular, CDPD, satellitesystems, millimeter wave or microwave systems, acoustic, and infrared(i.e., IrDA).

Overview

The present invention discloses inter alia methods and apparatus forproviding optimized performance for transceivers in multipleantenna/multiple air interface systems. In one exemplary implementation,the apparatus comprises a wireless communication device having two airinterfaces: (i) a personal area network (PAN) interface such as aversion of the Bluetooth protocol suite or other such technology (e.g.,IEEE Std. 802.15.1, 802.15.3, and so forth); and (ii) a wireless localarea network (WLAN) interface such as an interface compliant with theIEEE Std. 802.11 a/b/g/n specification, and the multiple antenna systemis a Multiple In-Multiple Out (MIMO) system as specified in the 802.11nspecification.

As previously noted, prior solutions to mitigating the effects ofinterference between two co-located air interfaces have not explicitlyconsidered the case of spatial diversity (i.e., MIMO). In such a case,the isolation between various antennae within the diversity group maynot be symmetric, and hence the methods and apparatus of the presentinvention seek to address this prior art shortcoming. This isaccomplished in one embodiment through use of a software algorithm whichevaluates the operational status of various components (e.g., whetherthe PAN interface is active), and whether overlapping spectrum is used,and based on the isolation characteristics of the various PAN and WLANantennae, selects either a MIMO or SISO mode of operation for the WLANinterface.

Additionally, the methods and apparatus of the present invention areparticularly useful in devices that cannot either achieve high isolationbetween the various antennae due to size restrictions (i.e., theenclosure or form factor is simply not large enough to provide thenecessary level of isolation). Such devices may include for example verysmall or thin-profile laptop computers or even some handheld devices.This need is particularly acute where other factors besides theaforementioned space restrictions come into play for antenna isolation;e.g., use of more than a 2×2 MIMO configuration (e.g., 3×3), use of ametal housing for the device, and/or use of yet added or different airinterfaces (e.g., WiMAX, GPS, UWB, etc.).

Moreover, the present invention advantageously does not require the useof time-sharing approaches as in the prior art. Specifically, aspreviously discussed, WLAN/Bluetooth time-sharing is a popular solutionfor most small form factor systems, yet has a pronounced negative impacton WLAN overall network capacity (even with WLAN “power saving mode”activated), and can cause additional unwanted complexity in managingwhich interface gets access to the spectrum when. In contrast, themethods and apparatus of the present invention allow simultaneous(non-time divided or shared) WLAN and Bluetooth operation, with littleor no adverse effect on WLAN network capacity.

The present invention further provides savings of platform power (e.g.,reduces battery drain in mobile devices) by avoiding unnecessarycollisions. By using a SISO mode and Bluetooth simultaneously, one WLANTx/Rx chain is powered off, which saves WLAN total power. As the SISOand Bluetooth antenna isolation is maintained at a reasonable and usefullevel, collision between the interfaces are minimized.

Business methods associated with the foregoing technology are alsodescribed.

Detailed Description of Exemplary Embodiments

Exemplary embodiments of the present invention are now described indetail. While these embodiments are primarily discussed in the contextof BT and WLAN (e.g., IEEE-Std. 802.11) coexistence scheme, it will berecognized by those of ordinary skill that the present invention is notlimited to any two particular wireless protocols. In fact, theprinciples discussed herein are equally applicable to any number ofwireless protocols which at least partly share frequency spectrum, andwith which antenna isolation or spectrum bandwidth problems occur as aresult of the two or more wireless protocol implementations beingsubstantially co-located with one another. For example, the Apple TV™digital media receiver sold and marketed by the Assignee hereof,utilizes both WLAN 802.11 and wireless universal serial bus (USB) airinterfaces. The WLAN and wireless USB interfaces share the same spectrum(i.e., ISM band), and hence could also benefit from the coexistencesolutions discussed subsequently herein. Similarly, devices having WiFiand WiMAX (IEEE Std. 802.16) interfaces, whether with or without a PANinterface, may also benefit. Similarly, a cellular data interfaceoperating in the same spectrum (e.g., EV-DO or similar, such as theUM-150 broadband access device offered by Verizon™) Myriad othercombinations of different air interfaces utilizing at least a portion ofthe same spectrum will also be recognized by the ordinary artisan giventhis disclosure.

Additionally, it will be appreciated that the methods and apparatus ofthe invention may be applied to situations where more than twointerfaces are co-located or proximate, but not necessarily operated allat the same time. For instance, in one variant of the invention, a userdevice is configured with three (3) distinct air interfaces (labeled“A”, “B” and “C” for purposes of this discussion), yet the most commonoperating mode for the user device is where only two of the threeinterfaces are operated simultaneously. Depending on which of the threeinterfaces are being operated at a given time, the policies or rulesapplied may be different. For example, interface A might havesignificant mutual interference issues with interface B, but not withinterface C. Similarly, interface C might have significant issues withinterface B, but not A. So, the present invention explicitlycontemplates the dynamic selection and application of one or moreoperating policies or configurations based on a determination of whichinterfaces are operating at a given time.

Antenna Isolation—

FIG. 1 shows an exemplary wireless device 100 having two RF modules: (i)a first module 102, representing a WLAN air interfaces, connected to afirst antenna pair (i.e., antenna 104 and another antenna 106); and (ii)a second RF module 112 connected to another antenna 114 and representinga PAN (personal area network) air interface. FIG. 1 shows that theantenna 104 of the WLAN air interface pair and antenna 114 of the PANair interface have a certain isolation 108 separating them. Similarly,antenna 106 and antenna 114 are separated by another isolation 110.Because RF isolation is often dependent on the placement of the antenna,the values of the isolations 108, 110 will often be comparable or evenequal to each other. This layout of antennae is termed as the “symmetricisolation” case for purposes of this discussion. In general, thesymmetric isolation case may include antenna configurations wherein thevalue of isolation between each antenna of a first RF interface arewithin a prescribed range or threshold (e.g., D1) of each other.

Symmetric isolation may further have different subtleties associatedtherewith. For example: (a) isolation 108 and isolation 110 may each berelatively small and below a low threshold (e.g., 15 dB); (b) isolationsbetween all WLAN antennae (104, 110) and the PAN antenna 114 are below amedium threshold (e.g., 30 dB); and (c) isolations between each of theWLAN antennae and the PAN antenna are above a high threshold (e.g., 35dB).

Some wireless devices may not exhibit the symmetric isolation describedabove. In such devices, due to the placement of antennae and/orinterposed or proximate components for example, differences in theisolation between antenna pairs may exceed the prescribed threshold(D1). This is referred to as an “asymmetric isolation” case.

FIG. 2 shows an exemplary wireless device 200 exhibiting asymmetricisolation. The wireless device 200 has two RF modules: (i) a first RFmodule 202, representing a WLAN air interfaces, connected to an antenna204 and another antenna 206, and (ii) a second RF module 212 connectedto antenna 214 and representing a PAN air interface. FIG. 2 shows thatantenna 204 of the WLAN air interface and antenna 214 of the PAN airinterface have a given isolation 208 separating them. Similarly, antenna206 and antenna 214 are separated by another value of isolation 210. Thevalues of the two isolations 208, 210 may significantly differ from oneanother due to any number of factors. Note that when antennae of awireless device 200 are placed in asymmetric isolation, some antennapairs may still have fairly high isolation between them (generally adesired feature). For example, the antennas 204, 214 in FIG. 2 may havehigh isolation between them, and the antennas 204, 210 may have highisolation between them also, but the antennas 214, 210 may have a lowisolation between them.

Antenna isolation may also depend on the design of the RF circuitry ofthe air interfaces. For example, some embodiments may employ a dynamicattenuator in front of the RF circuitry to attenuate incoming RF signal.Such a dynamic attenuator circuit may be configured to provide e.g., aconstant power input signal to a low noise amplifier (LNA) block of theRF front end that receives incoming signals. Isolation between antennaemay therefore change, responsive to the level of isolation applied bythe RF circuitry, so as to optimize receipt of data. Therefore, ingeneral, antenna isolation may have at least two components: (i) afixed, “layout based” component; and (ii) a variable dynamic attenuatorbased component.

Methods—

FIG. 3 shows a flowchart illustrating one exemplary embodiment of awireless “coexistence” method 300 in the context of a wireless device(e.g., the device 200 of FIG. 2).

At step 302 of the method 300, the wireless device 200 determines the RFisolation among various antennae present on the wireless device 200. Ingeneral, the wireless device 200 may have M air interfaces, where M=1,identified as I₁ through I_(M). Each air interface will in turn have oneor more transmit antennas and one or more receive antenna (which mayphysically be the same antenna). The term T_(k) represents the number oftransmit antennae for the k^(th) air interface I_(k), and the term R_(k)represents the number of receive antennae for the kth interface I_(k).The step 302 of determining the isolation may generally involve lookingat each pair of antenna for each of interface I_(k) and I_(n) where k≠n,and pairing up each of T_(k) transmit and R_(k) receive antennae fromthe k^(th) interface with each of T_(n) transmit and R_(n) receiveantennae on the n^(th) interface. For each antenna pair—an antenna fromthe k^(th) air interface and an antenna from the n^(th) interface, thecalculation for determining isolation may involve two steps.

First, the wireless device 200 may have pre-existing informationregarding placement of these antennae on the device and the resultingisolation. This a priori information, for example, may be calculated bya designer of the wireless device and programmed in the isolationcalculation algorithm (software or firmware) or stored in an onboardstorage device (e.g., memory). The contribution of this component of theisolation depends on the physical placement of the antennae, and maylargely be time invariant.

Second, the wireless device 200 may calculate a time-variant componentof the isolation between the two antennae. The time-variant componentmay depend on operational settings of the front-end circuitry connectedto each of the antennae for which the isolation is being determined. Itis well known in the art that front-end circuitry may employ atechnique, commonly known as “dynamic attenuation”, to change the gainof received signal. The dynamic attenuation may in turn depend on thesetting of an automatic gain control (AGC) circuit. Generally speaking,when the dynamic attenuator is set for higher attenuation setting, thiswill result in better isolation from an interfering antenna because theinterference will be attenuated more by the dynamic attenuator. Thewireless device 200 may be configured to obtain an attenuator settingfrom the front-end radio circuitry, where signal processing techniquessuch as the AGC are implemented, for one or more of the air interfacesof the device 200.

Using the isolation values among the antenna pairs, the wireless device200 may then decide whether the device currently has symmetric orasymmetric attenuation. For example, in one exemplary embodiment of theinvention, the wireless device 200 may decide that it is currentlyoperating in “symmetric attenuation” mode if it is determined that:

-   -   (1) the isolation between each antenna of air interface k and        each antenna of air interface n is below a prescribed low        threshold (e.g., 15 dB). The low threshold may be dependent for        example on the design of front-end circuitry of air interfaces k        and n; OR    -   (2) the isolation between each antenna for air interface k is        below a first “medium” threshold, and the isolation between each        antenna of air interface k and each antenna of air interface n        is below a second medium threshold. In one variant, the first        medium threshold and the second medium threshold are equal        (e.g., both equal to 30 dB), but they may also be different if        desired; OR    -   (3) if isolations as calculated in step (2) above are above a        designated “high” threshold (e.g., 35 dB).

It will be appreciated that the use of “static” thresholds in theexemplary embodiment above is for illustrative purpose only, and not adesign requirement. In another exemplary embodiment for example, thewireless device 200 may use different thresholds for different airinterfaces.

In a further embodiment, one or more of the threshold values may bedynamically varied based on e.g., then-prevailing operational conditions(such as the position of a movable portion of the device 200, such asthe “flip-up” screen portion of a laptop computer, or the open/closedposition of a clamshell-type mobile phone, which may affect theisolation or other relevant parameters).

In yet another embodiment, a wireless device 200 may not use thresholdsat all, but may use other quantitative measures in deciding whetherisolations are symmetric. Stated differently, the decision regardingwhether the layout of antennae is “symmetric” or “asymmetric” may itselfdepend on which ones of the techniques described herein results in ahigher (better) throughput on one or more of the air interfaces.

One important characteristic of symmetric attenuation is that individualisolations between antenna pairs are close enough to each other so thatwhen one examines different antennae of a first air interface from theperspective of an antenna of another (second) air interface, no antennais exceedingly “better” or exceedingly “worse” than other antennae ofthat first air interface in terms of isolation. Therefore, there may belittle if any incentive to treat one antenna preferentially over anotherantenna.

In step 304, the wireless device 200 may check if the current operationsof air interface k and interface n are such that their spectra areeither overlapping, or close enough to cause interference into oneanother. For example, the air interfaces may be both operating in theISM frequency band. This overlap may also be presumed based on e.g.,design parameters of the device, thereby obviating step 304. Forinstance, if Air Interface A is operating to transmit or receive, andAir Interface B is operating to transmit or receive at the same time asInterface A, then “overlap” may be presumed based on a priori knowledgeof the design parameters of each interface. However, in the case ofinterfaces which are more frequency-agile, or which various operatingmodes which may have differing spectral overlap with the other airinterface(s) such as Bluetooth adaptive frequency hopping (AFH) or thelike, then a more sophisticated analysis may be performed to determineif any meaningful or deleterious overlap will occur (and even theseverity thereof).

Step 304 may be device implementation-specific as well. For example,depending on the bandpass filter on the input side of an air interface,an interfering signal in the next channel (e.g., 24 MHz away) may or maynot detrimentally interfere with the wireless device 200.

If, in step 304, the wireless device decides that the current operationof the two antennae being evaluated for isolation is non-interfering,then in step 318, the wireless device may continue with isolationcalculations for the next antenna pair and may continue monitoring thecurrent antenna pair for any operational changes (e.g., frequency changeon one of the air interfaces).

Otherwise, the wireless device 200 may continue with step 318 ofcommunicating activity level at each antenna in the antenna pair to theother antenna (which may need be only one-way in the case of a BT/MIMOWLAN antenna pair; i.e., from BT to WLAN). In some embodiments, thewireless device 200 may be configured to communicate the activity levelat all times, but may use the activity level only when overlappingspectrum is detected in step 304 (and an appropriate isolation conditionis determined in step 302).

Additionally, the activity level of the interface itself can be used asa basis of determining whether a given antenna element (or set ofelements) is/are in operation (e.g., BT_Active for a Bluetoothinterface). If the interface is off, then the antenna are surely notradiating or receiving signals. However, the converse is not alwaystrue; i.e., if the interface is “on”, it none-the-less may still not beradiating or receiving signals (e.g., it may be in a sleep mode or othersuch state).

The wireless device 200 may achieve the communication in step 308 eitherby a hardware signal, by a software signal, or by any combination orhybridization of the two. In one embodiment, a signal line (or multiplesignal lines) may be configured between the antenna pair to carryactivity level signals (e.g., changes in voltage or current level). Thewireless device 200 may be configured to convey activity as a binaryvariable: e.g., Activity “ON” from antenna A to antenna B indicates thatantenna A is using its air interface for transmitting (or receiving) asignal, while Activity “OFF” may in turn indicate that antenna A is notusing its air interface, and is therefore not emitting or receiving anysignal. In some embodiments, the wireless device 200 may be configuredto communicate activity level in step 308 as a software signal. Thiscommunication may be implemented using any of the well-known softwaretechniques including, but not limited to, inter-process signals, mutex,pipes, application programmer interface (API) call, a flag setinstruction execution, write to or read from a storage location,transmitted message or packet, or other such mechanism. Any number ofdifferent approaches will be recognized by those of ordinary skill giventhe present disclosure.

One embodiment of the present invention utilizes a software signalingmechanism to make one air interface (e.g., WLAN) aware of the activityor activity level of the other air interface (e.g., Bluetooth). Broadlyspeaking, such a software embodiment may be either use “push” or a“pull” model. In “push” model, one radio interface may “push” itsinformation to the other radio interfaces. In response to the signal,the other radio interface may then take actions such as changing antennause, and so on. In “pull” mode, a radio interface may, from time totime, check on activity of other radio interfaces (e.g., by periodicpolling or the like) to see if any action needs to be taken.

It will be recognized that these push/pull models can be used in tandemif desired, such as where a first interface utilizes a “push” model withrespect to providing its information to the second interface, whileusing a pull model with respect to obtaining information from the secondinterface. Moreover, the various techniques may be used selectively bythe same interface during different operational circumstances.

In one variant of the invention, signaling from the PAN to the WLANinterface is used for effecting the MIMO to SISO switch. However, othersignals may be employed as well, such as for example where the WLANinterface sends signals to the PAN interface for other purposes such asdebug or “wake-up” based on the WLAN signal. Similarly, signals from thePAN interface to the WLAN may be utilized, such as for example when thePAN enters a sleep mode, it may inform the WLAN of this state change.

Returning again to FIG. 3, in step 316, the wireless device 200 may usethe information regarding attenuations between all antenna pairs toconfigure use of the antennae in a variety of different ways. In oneembodiment, the wireless device turn offs or on antennae (and anyassociated transmit/receive circuitry, or “chain”) as shown in, Table 1.For example, if the PAN air interface is idle (corresponding to thesecond row of Table 1), then the WLAN device may be configured tooperate in MIMO configuration both when WLAN operates in a overlappingor in a non-overlapping spectrum. On the other hand, if PAN airinterface is active, corresponding to the third row of Table 1, WLANinterface may be configured to operate in MIMO mode when operating innon-overlapping spectrum and SISO mode when operating in overlappingspectrum.

TABLE 1 WLAN: non-overlapping WLAN: PAN spectrum Overlapping spectrumIdle MIMO MIMO Active MIMO SISO

Table 2 shows exemplary decision table implemented in step 316 of themethod 300 by a wireless device 200 for a system with 3 transmit/receiveantennae. The first three columns of Table 2 indicate the relativeisolation of each WLAN antenna from the PAN antenna. As shown in row 2,when each antenna isolation is high, the WLAN air interface is operatedin 3×3 MIMO mode. However, in row 3, when two antennae have highisolation, but one does not, the wireless device 200 may choose tooperate the WLAN air interface in 2×2 MIMO mode by turning off thefront-end circuitry for the third (lower isolation) antenna. Row 7 showsanother decision possibility; i.e., when isolation of each antenna islow. In this case, the WLAN device 200 may choose to operate the WLANair interface in 3×3 MIMO, because it may not be possible to exploit anyadvantage of turning off some antenna while still maintaining highthroughput on the WLAN interface.

TABLE 2 Antenna 1 Antenna 2 Antenna 3 Operational mode isolationisolation isolation when PAN active High High High 3 × 3 MIMO High HighLow 2 × 2 MIMO High Low Low 1 × 1 SISO High Low High 2 × 2 MIMO Low HighHigh 2 × 2 MIMO Low High Low 1 × 1 SISO Low Low Low 3 × 3 MIMO Low LowHigh 1 × 1 SISOIn the context of the exemplary WLAN and Bluetooth device configuration,once the WLAN interface receives commands from the Bluetooth interfaceindicating its activity (either by software or hardware), then the WLANinterface will control its input/output RF chain by commands, such asfor example:

-   -   Power chain 1 on, chain 2 on:    -   apple80211-power=on,on    -   Power chain 1 off, chain 2 on:    -   apple80211-power=off,on

FIG. 3 a provided herein illustrates one alternate embodiment 320 of themethodology of FIG. 3, based on various optional determinations andmeasurements previously described herein with respect to FIG. 3.

Note that an additional operational advantage of the method proposed inthe present invention is that the wireless device 200 can reduce powerconsumption (and hence lengthen battery charge life on mobile devices,which is a critical attribute in many cases) by turning off one of theantenna and the corresponding signal processing circuitry, such aswithin the aforementioned WLAN MIMO configuration. This also helpsmitigate communications collisions between the interfaces. For example,in the exemplary case of a WiFi (WLAN) and Bluetooth coexistence scheme,it is estimated that such switching can save on the order of 20-30% ormore of power consumption. In theory, such a feature could save almosthalf (50%) of WLAN peak power, based on a typical WLAN interfaceconsuming about 2 W at peak power, and switching to a consumption of 1W-1.5 W. This level of power savings is quite significant, especiallyfor small devices where power storage capability (e.g., battery size) islimited.

The power savings thus achieved can be even more significant in someaspects; i.e., other than merely benefits in terms of reduced powerconsumption. For example, if an antenna is not turned off, the wirelessdevice 200 might sense higher interference on the WLAN communicationchannel. In some implementations, this may result in the physical layertransmission rate being dropped to a lower value, which can produce alonger transmission time for transmission of a packet or given amount ofdata. This in turn may, in some situations, make the transmission morevulnerable to corruption, thereby resulting in further drop in thephysical layer transmission rate (especially if retransmissions areimposed). The present invention avoids this “death spiral” phenomenon byturning off one or more antennae, thereby keeping the physical layertransmission rate from experiencing such an accelerated degradationmechanism.

It will also be recognized that the methods and apparatus describedherein may be used consistent with the methods and apparatus describedin co-owned and co-pending U.S. patent application Ser. No. 12/006,992filed Jan. 7, 2008 and entitled “Methods and Apparatus for WirelessDevice Coexistence” and Ser. No. 12/082,586 filed Apr. 11, 2008 entitled“Methods And Apparatus For Network Capacity Enhancement For WirelessDevice Coexistence”, each of the foregoing incorporated herein byreference in its entirety, depending on the type of platform and thedesired attributes. For example, in one embodiment, the MIMO/SISOswitching described herein can be used in a complementary fashion to theWLAN/Bluetooth control mechanisms specified in application Ser. No.12/082,586 referenced above so as to avoid adverse impacts on WLAN datarate from two possible sources (e.g., (i) competing Bluetooth “loading”of the ISM spectrum due to use of wireless headset, keyboard, mouse,etc., and (ii) interference due to operation in MIMO mode underasymmetric isolation conditions). Other combinations of complementaryfunctionality using the foregoing techniques will also be appreciated bythose of ordinary skill given the present disclosure.

Example: Bluetooth and 802.11b/g/n WLAN Coexistence—

Consider a wireless device 200 that has been configured with a Bluetoothinterface and a WLAN interface, both using the well-known ISM frequencyband. Further assume that in this exemplary embodiment, one antenna isused for Bluetooth transmission/reception, and 2×2 MIMO configuration isused for the WLAN air interface. Because it is a 2×2 system, the WLANinterface utilizes two transmitting antennae and two receiving antennae.

FIG. 4 shows exemplary (simulated) receiver performance of the WLAN airinterface of the above-described device 200 in the presence of Bluetoothtransmissions. In this example, one WLAN antenna has about 45 dBisolation from the Bluetooth antenna, and the other WLAN antenna hasabout 15 dB isolation from the Bluetooth antenna. For these simulations,the Bluetooth transmitter is transmitting at a power level of 4 dBm, andat data rate of 130 Kilobytes per second (it is noted that yet higherrates may also be achievable, and the aforementioned rate is merely forpurposes of illustration). The uppermost curve 402 of FIG. 4 shows thereceiver performance of the WLAN air interface as a function of transmitpower (X-axis or abscissa of FIG. 4) when the Bluetooth transmission iscompletely turned off; that is, there is no interference between theBluetooth and WLAN interfaces. When Bluetooth transmission is turned on,the curve 404 of FIG. 4 shows degradation in data throughput at the WLANinterface as a function of transmitted power, assuming that the WLANinterface continues operating in a MIMO configuration.

The curve 406 of FIG. 4 shows that data throughput can be improved byoperating the WLAN interface in SISO mode; i.e., by turning off theantenna with the lower isolation with the Bluetooth interface, andoperating only with the antenna with higher isolation.

FIG. 5 shows exemplary transmission performance of the WLAN airinterface of the device 200 in the presence of Bluetooth transmissions.In this example, one WLAN antenna has about 45 dB isolation from theBluetooth antenna, and the other WLAN antenna has about 15 dB isolationfrom the Bluetooth antenna. The uppermost curve 502 of FIG. 5 showstransmitter performance of the WLAN air interface as a function of thetransmit power (X-axis or abscissa) if the Bluetooth transmission iscompletely turned off (that is, there is no interference between theBluetooth air interface and the WLAN interface). When Bluetoothtransmission is turned on and transmitting at power level 4 dBm and atdata rate 130 Kilobytes per second (again, higher rates may also beachievable, and the aforementioned rate is merely for purposes ofillustration), the curve 504 of FIG. 5 shows degradation in datathroughput at the WLAN interface, as a function of transmitted power,assuming that the WLAN interface continues operating in MIMOconfiguration. The curve 506 of FIG. 5 shows that throughput can beimproved by operating the WLAN interface in SISO mode, by turning offthe antenna having the lower isolation with the Bluetooth antenna, andoperating only with the antenna with the higher isolation.

The above simulation model results show that under certain situations,when a MIMO air interface is experiencing interference from anotherantenna, it is preferable to shut down the antenna at which interferenceis stronger because of relatively poor isolation from the interferingsource. If the interfering signal is of sufficiently high power asmeasured at the relevant antenna (as might be the case when isolation ispoor), it may saturate the signal level at the receiving antenna,causing the receiving antenna to attenuate incoming signals. This mayresult in desirable signals being attenuated as well.

Furthermore, high power levels of interfering signal due to poorisolation could also result in damage to the front end of the radioreceiver. In such a case, even if another antenna in the MIMO system hasgood isolation with the interfering source, its operation may have to becompromised. In such cases, it might be preferable to completely turnoff the antenna with poor isolation, and operate the MIMO air interfacewith one less antenna. For example, a 2×2 MIMO system may be scaled backto operate in 1×1 (SISO) mode, a 3×3 antenna system may be scaled backto operate in 2×2 mode, and so forth.

Wireless Apparatus—

FIG. 6 shows a block diagram of an exemplary implementation of awireless device 200 of the type previously described herein, wherein themethods of the invention are implemented. As shown in FIG. 6, a signalbus 602 communicatively connects a central processor unit (CPU) 608, amemory unit 606 and two RF “front-ends” (Front-End 1 (614) and Front-End2 (612)) to each other, each of the foregoing rendered in the form ofintegrated circuits disposed on a substrate such as an FR-4 circuitboard or the like. Front-end 1 614 is communicatively connected to afirst air interface 604 and Front-End 2 612 is communicatively connectedto a second air interface 610. A signal 616 between the two front-ends612, 614 may be used to communicate the activity signal. In someembodiments, this signal 616 may not be present in hardware, but may beimplemented in software as previously described herein.

The wireless device 200 of FIG. 6 may comprise for example a mobiletelephone or smartphone, laptop computer, PDA or other hand-held device,or in fact any device having multiple air interfaces with the potentialfor interference. For instance, even residential or enterprise basestations may utilize the technology described herein for management ofinterference among its multiple air interfaces if so equipped. Thepresent invention is accordingly no way limited to a particularapplication (communications versus data), location or use (mobile versusfixed), or function (transmitter versus receiver).

Test Results—

FIG. 7 shows an exemplary configuration of a test setup 700 useful inaccordance with the invention. Specifically the setup 700 of FIG. 7might be used where testing and adaptation to the configuration of aparticular device are required. For example, the test setup may be usedto generate graphs of the type shown in FIGS. 4 and 5. A wireless deviceunder test (DUT) 702 includes two or more air interfaces (e.g., a WLANmodule 704 and a Bluetooth module 706). The WLAN module 704 communicateswith a WLAN access point (AP) 708. One antenna is simulated byconnecting one terminal on the WLAN module 704 to the WLAN AP 708through an attenuator 714 and a splitter 720. The other antenna of theWLAN module 704 is simulated by connecting the second terminal of theWLAN module 704 to the second terminal of WLAN AP 708 through splitters760 and 720 and variable attenuator 712. The attenuators 714 and 712simulate the RF signal path loss in the WLAN network. The Bluetoothmodule 706 is connected to the Bluetooth system 710 through the splitter728 and a variable attenuator 730. The Bluetooth module 706 also causesinterference to the first terminal of WLAN module 704 through itsconnection via splitter 728, variable attenuator 726, and splitters 724and 720. The Bluetooth module 706 causes interference at the secondterminal of WLAN module 704 through the splitters 728, 724 and 716 andvariable attenuators 726 and 722. If all splitters are assumed to haveabout the same signal attenuation, then the variable attenuator 722represents the additional isolation between simulated antenna of theBluetooth module 706 and simulated antennae of the WLAN module 704.Various performance curves, such as ones shown in FIGS. 4 and 5, canconveniently be generated and evaluated using this test setup.

Methods of Doing Business—

In another aspect of the invention, methods of doing business relatingto the aforementioned apparatus and methods are disclosed.

In one embodiment (see FIG. 8), the method 800 comprises providing(e.g., selling for valuable consideration) portable computers such aslaptops, PDAs, smartphones, or other client devices or services (e.g.,the Apple MacBook Air™ laptop computer, or Apple TV™ set-top box andservice, provided by the Assignee hereof) that include the MIMO/SISOswitching and optimization features discussed previously herein.Specifically, as shown in FIG. 8, the client device configuration isfirst determined per step 802, including selection of various options bya consumer. This may be accomplished for example via the Internet (e.g.,using an on-line configuration interface or “wizard” or routine) whichallows the customer to configure their prospective device according toany number of different options (“builds”). For instance, one user maywant a Bluetooth and WiFi (802.11n) build in a very space-constraineddevice, such as the Macbook Air computer manufactured by the Assigneehereof.

At step 804, based on the user's inputs as step 802, the device isconfigured, including selecting from two or more different antennaplacement locations. In space-constrained applications such as theaforementioned Macbook Air device, these location choices may belimited. These choices may be further restricted by other factors, suchas the use of a metallic casing (housing) on the device. For instance,in a device having an almost entirely metallic housing such as theMacbook Air, the available choices for both Bluetooth and WLAN (MIMO)antenna placement are quite limited, including locations on or proximateto the hinge assembly between the “clamshell” portions of the housing.So, for example, where the user requests a WLAN interface only, the two(or more) MIMO antennae of the WLAN interface could be disposed anywherealong that hinge assembly (other restrictions permitting), since nointerference with another indigenous interface would occur. However,when a Bluetooth or other such interface is added to the build, theasymmetric isolation previously described must be considered, and hencelocations for the two (or more) WLAN MIMO antennae and the Bluetoothantenna would need to be coordinated so as to maintain adequate WLAN/BTisolation for at least one of the WLAN MIMO antennae. If a 3×3 MIMOarrangement were used, yet another placement pattern would be mandated,as would be the case if a third air interface (e.g., WiMAX or UWB) wereadded as well.

At step 806, the device is built according to the user's selectedconfiguration and the antenna placement requirements of step 804.Moreover, as part of step 806, the device hardware/software may beconfigured (e.g., programmed) with the isolation data relating to theselected antenna configuration. For instance, if a certain WLAN MIMO andBT antennae element placement were mandated by the MIMO/SISO switchingand optimization requirements, then test values obtained from aprototype device so configured (e.g., obtained using the test rig ofFIG. 7) could be loaded into memory, EEPROM, etc. so that theswitching/optimization algorithm (see FIGS. 3 and 3 a) would know whatthe isolation was between various of the antennae for differentoperating conditions. This approach advantageously obviates the need todiscover or measure the actual isolation of the device being built(i.e., the prototype is presumed to accurately reflect the condition ofall subsequently manufactured production devices), but does have thedrawback that the latter approach can dynamically detect anyconfiguration changes (such as the addition of a WiMAX card or otherpotentially interfering device) after manufacture, and ostensibly adaptthe operation of the MIMO/SISO switching algorithm accordingly.

In another aspect of the business method, consumers may bring back theiralready purchased client devices (e.g., laptops, smartphones, PDAs,etc.) for or after reconfiguration so as to have them “re-optimized” forthe new configuration. This may include relocating one or more of theirMIMO antennae so as to provide the aforementioned asymmetry inisolation.

Alternatively, the user's device may be configured with its ownindigenous evaluation/optimization capability as previously describedabove. For example, a laptop user might install a WiFi (802.11n) cardthemselves if their production device was not so equipped. With the newcard, there may be significant interference with another existing orco-installed air interface, hence requiring MIMO/SISOswitching/optimization according to the methods described herein.

It will be recognized that while certain aspects of the invention aredescribed in terms of a specific sequence of steps of a method, thesedescriptions are only illustrative of the broader methods of theinvention, and may be modified as required by the particularapplication. Certain steps may be rendered unnecessary or optional undercertain circumstances. Additionally, certain steps or functionality maybe added to the disclosed embodiments, or the order of performance oftwo or more steps permuted. All such variations are considered to beencompassed within the invention disclosed and claimed herein.

While the above detailed description has shown, described, and pointedout novel features of the invention as applied to various embodiments,it will be understood that various omissions, substitutions, and changesin the form and details of the device or process illustrated may be madeby those skilled in the art without departing from the invention. Theforegoing description is of the best mode presently contemplated ofcarrying out the invention. This description is in no way meant to belimiting, but rather should be taken as illustrative of the generalprinciples of the invention. The scope of the invention should bedetermined with reference to the claims.

1. Apparatus having multiple air interfaces, comprising: a plurality offirst antenna elements configured to communicate on a first airinterface; at least one second antenna element configured to communicateon a second air interface; first front end circuitry operatively coupledwith said plurality of first antenna elements, said first front endcircuitry enabling transmitting and receiving signals over said firstair interface; second front end circuitry operatively coupled with saidat least one second antenna element, said second front end circuitryenabling transmitting and receiving signals over said second airinterface; a communication channel between said first air interface andsaid second air interface and adapted to carry activity information; anda processor communicatively coupled to said first front end circuitryand said second front end circuitry; said processor configured to:determine an isolation between antennae pairs formed from said pluralityof first antenna elements and said at least one second antenna element;evaluate whether said isolations are symmetric or asymmetric; and basedat least in part on said evaluation, not using of at least one antennaelement from said plurality of first antennae.
 2. The apparatus of claim1, wherein said first front end circuitry comprises front end circuitsfor each of said antenna elements of said plurality, and said not usingcomprises turning off at least a portion of said front end circuits. 3.The apparatus of claim 1, wherein said not using comprises not using ifsaid isolations are evaluated to be asymmetric.
 4. The apparatus ofclaim 1, wherein said apparatus comprises a portable computerized devicehaving a substantially metallic outer case.
 5. The apparatus of claim 1,wherein said first air interface comprises a wireless local area network(WLAN) interface having multiple-input multiple-output (MIMO)capability, and said second air interface comprises a personal areanetwork (PAN) interface.
 6. The apparatus of claim 5, wherein theplacement of said plurality of first antenna elements of said WLANinterface and said at last one second antenna element of said PANinterface within said apparatus does not permit isolation levels betweensaid plurality of first elements and said at least one second elementsufficient for simultaneous operation of all of said plurality of firstelements and said at least one second element without significantdegradation of a data rate of said WLAN interface.
 7. The apparatus ofclaim 1, wherein said processor is configured to detect said isolationsas a function of at least one of: (i) the physical placement of saidplurality of first antenna elements; (ii) an operational setting of saidfirst front end circuitry; and (iii) an operational setting of saidsecond front end circuitry.
 8. The apparatus of claim 1, wherein saidcommunication channel comprises one or more hardware-based channelsadapted to carry signals from said second air interface to said firstair interface.
 9. Wireless portable apparatus adapted for datacommunication over first and second air interfaces, the apparatuscomprising: a first air interface having at least two antennaeassociated therewith; a second air interface having at least one antennaassociated therewith, said first and second air interfaces operating ina substantially overlapping frequency band, said at least two antenna ofsaid first air interface being disposed within said apparatusasymmetrically with respect to their isolations with said at least oneantenna of said second air interface; a processor; and a storage device,said storage device comprising a computer program having a plurality ofinstructions that when executed: determine if a potential forinterference between said first and second air interfaces exists; and ifsaid potential exists, turning at least one of said at least twoantennae off so as to mitigate said interference.
 10. The apparatus ofclaim 9, wherein: said first air interface comprises a multiple-inputmultiple-output MIMO wireless LAN (WLAN) interface; said second airinterface comprises a personal area networking (PAN) interface; and saidturning at least one of said at least two antenna off comprisesdisabling transmission or reception via one of said at least twoantennae that has lower isolation with said at least one antenna of saidPAN interface.
 11. The apparatus of claim 10, wherein said apparatuscomprises a portable computerized device having a clamshell-like outercase, and said at least two antennae of said WLAN interface and said atleast one antenna of said second air interface are all disposedsubstantially within a hinge region of said clamshell-like case.
 12. Theapparatus of claim 11, wherein said outer case is substantiallymetallic.
 13. The apparatus of claim 9, wherein said determination ofthe potential for interference comprises determining whether both firstand second air interfaces are transmitting or receiving at the sametime.
 14. A method of operating a device having at least first andsecond air interfaces, the method comprising: communicating on the firstair interface via a plurality of first antenna elements; communicatingon the second air interface via at least one second antenna element; andwherein the first and second air interfaces are additionallycoordinating activity information via a distinct communication channel;determining isolations between antennae pairs formed from the pluralityof first antenna elements and the at least one second antenna element;evaluating whether the isolations are symmetric or asymmetric; and basedat least in part on the evaluation, enabling a subset of the pluralityof first antenna elements.
 15. The method of claim 14, wherein the firstair interface comprises a multiple-input multiple-output MIMO wirelessLAN (WLAN) interface, and the second air interface comprises a personalarea networking (PAN) interface.
 16. The method of claim 15, wherein thedevice comprises a mobile wireless device also having a cellular airinterface and an at least partly metallic outer housing.
 17. Wirelessportable apparatus adapted for data communication over first and secondair interfaces, the apparatus comprising: a first air interface havingat least two antennae associated therewith; a second air interfacehaving at least one antenna associated therewith, the first and secondair interfaces operating in a substantially overlapping frequency band,the at least two antenna of the first air interface being disposedwithin the apparatus asymmetrically with respect to their isolationswith the at least one antenna of the second air interface; a processor;and a storage device in data communication with the processor, thestorage device comprising a computer program having a plurality ofinstructions that are configured to, when executed on the processor:determine when a potential for interference between the first and secondair interfaces exists; and when the potential exists, turning at leastone of the at least two antennae off so as to mitigate the interference.18. The apparatus of claim 17, wherein: the first air interfacecomprises a multiple-input multiple-output MIMO wireless LAN (WLAN)interface; the second air interface comprises a personal area networking(PAN) interface; and the turning at least one of the at least twoantenna off comprises disabling transmission or reception via one of theat least two antennae that has lower isolation with the at least oneantenna of the PAN interface.